Hello Audentity
Yes I'd read that Paul McCartney quote somewhere too, maybe as much as a couple of years ago, but wasn't sure it wasn't some kind of joke or hoax! Nice if it's true though, and just goes to show how massively influential the great Gustav was.
For what it may be worth, the late great Deryck Cooke wrote an interesting article about the Lennon-McCartney songs which is in his posthumously-published book, "Vindications", which includes a short analysis of their song, "Yesterday".
A couple of months ago I visited the Beatles' houses in Liverpool and was absolutely astonished at what a tiny house Paul McCartney was brought up in. Amazing to think of such a great talent coming from so small a space.